Pulsed nanosecond fiber
lasers can weld, too!
LASER HAS USES IN SEVERAL MATERIAL PROCESSING TASKS
JACK GABZDYL and DANIEL CAPOSTAGNO
The versatility of pulsed nanosec- ond (ns) infrared fiber lasers is well known, as they are the laser of choice for the majority of industrial marking and engraving applications. Having typically less than a few millijoules in pulse energy and up to 100W of average power, they pack an impressive punch, with high pulse repetition rates and continuous-wave (CW) and modulated qua-si-CW (QCW) modes. More recently, they have begun to be
used for a variety of micromachining and surface texturing
applications and even for remote microcutting applications.
The vast majority of these applications involve material removal.
Based on this premise, considering this beam source for material joining is counterintuitive. To consider that the same source
can join material as well as remove, ablate, engrave, cut, and
mark is truly impressive (FIGURE 1).
To a laser user, the benefits are significant, offering access
to a laser source that can multi-task as well as be packaged
in a compact, often air-cooled form factor, making integration
seamless. Conventional wisdom suggests that long millisec-ond-type pulses with large pulse energies are needed to create welds and joints—well, evidently not! The capability of this
genre of laser for materials joining is less well known, but their
ability to join thin section materials is remarkable.
Globally, industries such as consumer electronics, energy
storage, and medical devices increasingly package more features into smaller-volume, high-density packaging. With that,
there is also an increasing need to create effective manufac-
turing technologies to make these products a reality; in this
case, with laser joining technologies. So there is a production
technology that offers the required high reproducibility, accuracy, and productivity with the all-important low cost (capital
and maintenance)—industrial (nanosecond infrared fiber) lasers
that meet the demands of the market.
A variety of laser types have all found their places, from
pulsed YAG, disk, fiber (CW and QCW), and even diode,
depending on the application. Until now, the use of nanosecond
pulsed lasers has been limited to a few
pioneering applications—but things
are changing, with recent applications
demonstrated using nanosecond fiber
lasers for material joining.
SPI has been a pioneer in the introduction of master oscillator
power amplifier (MOPA) nanosecond fiber lasers, which have
been viewed as extremely versatile tools because of their ability to control and tailor the pulse characteristics to the requirements of applications. This is achieved through the ability to
change the pulse duration and also the pulse frequency, with
some sources able to operate from 3 to 500ns. Their ability to
switch between pulsed and CW operation has also been an
important differentiator, as has the availability of these laser
sources in a range of different beam qualities, providing tools
that can be adapted to the job in hand. Within the range of the
average and peak powers, this laser can be modulated in the
millisecond regime for applications that demand a millisecond
pulse of low average power.
Take plastic welding, for instance: some applications where
precision is required, such as microfluidic devices, benefit from
the use of a fiber laser over other sources. The energy profile
in the spot can sometimes make the difference. For example,
in a complex medical device, where the requirement was to
weld a transparent polymer to a black one, a 40W M2= 3 laser
beam was used in CW mode (FIGURE 2). “It gave me the control of the beam in terms of spot size, energy distribution, and
FIGURE 1. The
compact SPI 100W
nanosecond water-cooled fiber laser.